As image forming apparatuses such as printers, facsimile apparatuses, copying apparatuses and composite (or multi-function) apparatuses having the functions of the printer, facsimile apparatus and copying apparatus, there are the so-called ink-jet recording apparatuses which use an ink-jet recording head, for example. The ink-jet recording apparatus makes an image formation on a recording medium by ejecting ink from the ink-jet recording head onto the recording medium. The recording medium may be paper, OHP film or any suitable recording sheet onto which the ink may be adhered. The image formation includes various kinds of recording and printing of characters, images and/or photographs. In the ink-jet recording apparatus, it is essential to provide a mechanism for maintaining and recovering the performance of the ink-jet recording head.
Main functions of this mechanism for maintaining and recovering the performance of the ink-jet recording head include a cap function, an ejection recovery function and a wiping function. The cap function covers the nozzle by a sealed cap member so as to prevent the recording ink in a vicinity of the nozzle from thickening and sticking due to natural evaporation. The ejection recovery function ejects the recording ink so as to eliminate poor ink ejection caused by air bubbles or the like generated within the nozzle, and draws out the recording ink from the nozzle under suction via the cap function, so as to recover the normal ink-jet performance. The wiping function wipes off the residual recording ink which is adhered on the nozzle surface and causes irregular ink-jet performance unless removed.
By using the above described mechanism to carry out the operation of maintaining and recovering the performance of the ink-jet recording head, the recording ink that is ejected from the recording head but not used for the recording (image formation) is ejected as waste ink. Japanese Laid-Open Patent Applications No.2000-127439 and No.2003-165236 propose ink-jet recording apparatuses provided with a waste tank or container (hereinafter simply referred to as a waste tank) for containing the ejected waste ink.
A Japanese Laid-Open Patent Application No.2001-171148 proposes a waste tank that is sectioned into a plurality of sections that are respectively provided with an absorbing member, so as to reduce the frequency of replacing the absorbing member. A Japanese Laid-Open Patent Application No.2002-19153 proposes a waste tank provided with an absorbing member that is divided into a plurality of replaceable parts, so as to enable reduction of the size of the ink-jet recording apparatus.
Japanese Laid-Open Patent Applications No.2002-307720 and No.2002-307705 propose integrally providing the waste tank and an ink cartridge, so that the waste tank is replaced simultaneously as the replacement of the ink cartridge.
If the waste tank becomes full and the waste ink overflows, this ink overflow causes undesirable effects within the ink-jet recording apparatus. For this reason, a full tank detection device is generally provided to detect whether or not the waste tank has become full.
A Japanese Laid-Open Patent Application No.2004-136550 proposes a full tank detection device which determines an amount of waste ink in the absorbing member of the waste tank by taking into account a total amount of ink supplied and an amount of ink that evaporates, and calculates a reference value based on which the full tank is detected based on the amount of waste ink. A Japanese Patent No.3167475 proposes a full tank detection device which determines the amount of waste ink in the absorbing member of waste tank by taking into consideration an amount of ink that evaporates depending on time intervals at which the waste ink is supplied into the waste tank, and calculates the reference value based on which the full tank is detected based on the amount of waste ink. A Japanese Laid-Open Patent Application No.2000-141704 proposes a full tank detection device which determines the amount of waste ink in the absorbing member of the waste tank by taking into account an amount of ink that evaporates depending on a number of times a maintenance is made, and calculates the reference value based on which the full tank is detected based on the amount of waste ink.
A Japanese Laid-Open Patent Application No.2004-66554 proposes an ink-jet recording apparatus provided with a plurality of waste tanks. The full tank detection device is provided with respect to only one of the plurality of waste tanks, and the amount of waste ink in the one waste tank that is detected by the full tank detection device is accumulated as a counted value. When the counted value reaches a value corresponding to the full tank, it Is judged that all of the waste tanks are full.
On the other hand, in order to realize a high-quality recording by the ink-jet recording apparatus on plain paper, there are ink-jet recording apparatuses that use a pigment-based ink. The pigment-based ink uses an organic pigment, carbon black or the like as a coloring agent. However, unlike dyes, the pigment is water insoluble. For this reason, the pigment is normally mixed with a dispersing agent, and a dispersion process is carried out so as to obtain a water ink in which the pigment is stably dispersed in water.
Such a pigment-based ink generally has a viscosity higher than that of a dye-based ink. As a result, the pigment-based ink easily thickens, and when the thickened pigment-based ink falls directly on the absorbing member In the waste tank, the thickened pigment-based ink easily forms a deposit on the absorbing member instead of being absorbed.
Therefore, if the pigment-based ink is used in combination with the conventional waste tank that is provided with the full tank detection device, there is a problem in that the pigment-based ink may form a deposit in a vicinity of an ink receiving opening in the waste tank and cause an overflow before the absorbing member is used up, because the full tank detection device cannot detect the full waste tank caused by such a deposit. In addition, since such a deposit prevents the pigment-based ink from evenly filling the entire waste tank, there is a problem in that the pigment-based ink may overflow from the waste tank before the pigment-based ink reaches a sensor of a hardware full tank detection device, particularly when the sensor is located at a position separated from the ink receiving opening in the waste tank.
Furthermore, in the case of a software full tank detection device which detects the full tank by software, the amount of waste ink that is supplied to the waste ink is determined or calculated, and the full tank is judged by comparing the amount of waste ink that is supplied with the reference value. Hence, it is necessary to stored in advance an amount of ink that is consumed for each of various kinds of operations including the ejection of the ink to remove air bubbles in the ink, the drawing out of the ink under suction to recover the ink ejection performance and the like. As a result, there is a problem in that a relatively complex operation is required to calculate the amount of ink consumed every time each of the various kinds of operations described above is carried out, to thereby deteriorate the throughput of the ink-jet recording apparatus.